1. Field of the Invention
The present invention relates to a heat exchanger with a thermoelectric conversion element module interposed between heat exchange bodies on a heat radiation side and heat exchange bodies on a heat absorption side and a manufacturing method thereof, and more particularly to reduction of thermal resistance in the heat exchanger and to improvement of the yield at the time of manufacturing the heat exchanger.
2. Description of the Related Art
In a semiconductor manufacturing apparatus (e.g., an etcher apparatus), a cooling medium, a chemical solution or the like is used. The cooling medium or the chemical solution requires its temperature control, so that a heat exchanger is used as an apparatus for temperature controlling. FIG. 5 is a diagram showing a structure of a basic heat exchanger.
A heat exchanger 20 includes heat radiation side and heat absorption side heat exchange bodies 2, 3 and a thermoelectric conversion element module 4 interposed between the heat radiation side heat exchange body 2 and the heat absorption side heat exchange body 3. The thermoelectric conversion element module 4 is comprised of heat radiation side electrodes 41, heat absorption side electrodes 42 and p-type and n-type thermoelectric conversion elements 43, 44 interposed between the electrodes 41, 42. The electrodes 41, 42 and the p-type and n-type thermoelectric conversion elements 43, 44 are connected serially in order of the heat radiation side electrodes 41, the n-type thermoelectric conversion elements 44, the heat absorption side electrodes 42, the p-type thermoelectric conversion elements 43, the heat radiation side electrodes 41, the n-type thermoelectric conversion elements 44, . . . .
The heat radiation side and heat absorption side heat exchange bodies 2, 3 and the thermoelectric conversion element module 4 must be electrically insulated from each other. Therefore, thin insulating layers 21, 22 of alumite or the like are respectively interposed between the heat radiation side heat exchange body 2 and the heat radiation side electrodes 41 and between the heat absorption side heat exchange body 3 and the heat absorption side electrodes 42. Adhesion between the heat radiation side electrodes 41 and the insulating layer 21 and between the heat absorption side electrodes 42 and the insulating layer 22 is made with grease 23, 24 or an adhesive between them.
Generally, the grease or the adhesive has thermal resistance which is relatively greater than that of a metal. Therefore, when the grease or the like is used for the heat exchanger, thermal conductivity drops, and heat exchange efficiency lowers. Especially, great heat quantity transfers on the heat radiation side of the heat exchanger. Therefore, when grease or the like is disposed on the heat radiation side, heat exchange efficiency lowers considerably. Compensation for the lowered quantity of the efficiency requires an increase in current, causing an increase in power consumption. Accordingly, there is developed a technology of lowering the thermal resistance of the heat exchanger in these years.
Japanese Patent No. 3510831 discloses a technology that adheres a heat exchange body and heat radiation side electrodes of a thermoelectric conversion element module without grease interposed between them. FIG. 6 is a diagram showing a structure of the heat exchanger disclosed in Japanese Patent No. 3510831.
According to the technology described in Japanese Patent No. 3510831, the alumina insulating coat 25 is formed on the surface of the heat radiation side heat exchange body 2 by spraying, and the metal coat 27 of copper, a copper alloy, nickel or the like is additionally formed on the surface of the insulating coat 25 by plasma spraying or metalizing. And, the metal coat 27 and the heat radiation side electrodes 41 of the thermoelectric conversion element module 4 are fixed by soldering. By configuring in this way, thermal resistance is reduced because no grease is interposed between the heat radiation side heat exchange body 2 and the heat radiation side electrodes 41.
According to the technology described in Japanese Patent No. 3510831, the alumina insulating coat 26 is also formed on the surface of the heat absorption side heat exchange body 3 by spraying. And, the insulating coat 26 and the heat absorption side electrodes 42 of the thermoelectric conversion element module 4 are adhered to each other with the grease 9 between them. The grease 9 is interposed to make the heat absorption side heat exchange body 3 slidable against the thermoelectric conversion element module 4. If the heat absorption side heat exchange body 3 is fixed to the thermoelectric conversion element module 4, the thermoelectric conversion element module 4 might be damaged when the heat absorption side heat exchange body 3 undergoes thermal expansion or contraction. Interposition of the grease between the thermoelectric conversion element module 4 and the heat absorption side heat exchange body 3 prevents the damage.
The heat radiation side and heat absorption side heat exchange bodies are made of a metal such as a cast or extrusion material. When cast or extruded, the heat radiation side and heat absorption side heat exchange bodies include cavities. The cavities in the surfaces of the heat radiation side and heat absorption side heat exchange bodies become small holes. And, the surfaces of the heat radiation side and heat absorption side heat exchange bodies might also have fine flaws and the like other than the cavities.
The cavities, flaws and the like in the surfaces of the heat radiation side and heat absorption side heat exchange bodies cannot be filled by alumina spraying disclosed in Japanese Patent No. 3510831. Therefore, insulation cannot be secured between the heat exchange bodies and the electrodes of the thermoelectric conversion element module because an insulating coat is not formed on any part of the surface having the cavities, flaws and the like. Such heat exchange bodies are judged defective and discarded in an insulation test stage. In other words, the technology of Japanese Patent 3510831 has a problem that the yield in the heat exchanger manufacturing becomes low.
The present invention has been made in view of the above circumstances and secures the insulation between the heat exchange bodies and the thermoelectric conversion element module and improves the yield when manufacturing the heat exchanger.